Light emitting diode, method of fabricating the same and led module having the same

ABSTRACT

A light emitting diode is provided to include a first conductive-type semiconductor layer; a mesa including a second conductive-type semiconductor layer disposed on the first conductive-type semiconductor layer and an active layer interposed between the first and the second conductive-type semiconductor layers; and a first electrode disposed on the mesa, wherein the first conductive-type semiconductor layer includes a first contact region disposed around the mesa along an outer periphery of the first conductive-type semiconductor layer; and a second contact region at least partially surrounded by the mesa, the first electrode is electrically connected to at least a portion of the first contact region and at least a portion of the second contact region, and a linewidth of an adjoining region between the first contact region and the first electrode is greater than the linewidth of an adjoining region between the second contact region and the first electrode.

CROSS REFERENCE TO RELATED APPLICATION

This patent document is a continuation-in-part of U.S. patentapplication Ser. No. 14/848,232, filed on Sep. 8, 2015, which claims thebenefits and priorities to the Patent Cooperation Treaty (PCT)Application No. PCT/KR2014/006904, filed on Jul. 29, 2014, which furtherclaims priorities from and the benefits of Korean Patent Application No.10-2013-0089414, filed on Jul. 29, 2013, and Korean Patent ApplicationNo. 10-2013-0089415, filed on Jul. 29, 2013. This patent document alsoclaims the benefits and priorities to Korean Patent Application No.10-2014-0195162, filed on Dec. 31, 2014, Korean Patent Application No.10-2015-0165706, filed on Nov. 25, 2015. The above applications are allhereby incorporated by reference for all purposes as if fully set forthherein.

TECHNICAL FIELD

Exemplary embodiments of the disclosed technology relate to a lightemitting diode (LED), an LED module including the same, and a method offabricating the same. For example, some implementations of the disclosedtechnology relates to a light emitting diode having improvedreliability, an LED module including the same, and a method offabricating the same.

BACKGROUND

Since GaN-based light emitting diodes were first developed, GaN-basedLEDs have been used for various applications including natural color LEDdisplays, LED traffic signboards, white LEDs, and the like.

Generally, a GaN-based light emitting diode is formed by growingepitaxial layers on a substrate such as a sapphire substrate, andincludes an N-type semiconductor layer, a P-type semiconductor layer andan active layer interposed therebetween. In addition, an n-electrode padis formed on the N-type semiconductor layer and a p-electrode pad isformed on the P-type semiconductor layer. The light emitting diode isconnected to an external power source through the electrode pads anddriven thereby. In this case, current flows from the p-electrode pad tothe n-electrode pad through the semiconductor layers.

On the other hand, a flip-chip type light emitting diode is used toprevent light loss due to the p-electrode pad while improving heatdissipation efficiency, and various electrode structures are proposed topromote current spreading in a large area flip-chip type light emittingdiode. Examples are disclosed in U.S. Pat. No. 6,486,499. For example, areflective electrode is formed on the P-type semiconductor layer, andextension legs are formed on a region of the N-type semiconductor layer,which is exposed by etching the P-type semiconductor layer and theactive layer, to facilitate current spreading.

The reflective electrode formed on the P-type semiconductor layerreflects light generated from the active layer to improve lightextraction efficiency and helps current spreading in the P-typesemiconductor layer. On the other hand, the extension legs connected tothe N-type semiconductor layer help current spreading in the N-typesemiconductor layer to allow uniform generation of light in a wideactive region. Particularly, a light emitting diode having a large areaof about 1 mm² and used for high power output requires current spreadingnot only in the P-type semiconductor layer but also in the N-typesemiconductor layer.

On the other hand, a forward voltage Vf is supplied to the lightemitting diode to generate light, and a light emitting diode having goodluminous efficacy refers to a light emitting diode capable of emittingthe same intensity of light at a lower forward voltage. Therefore,various attempts have been made to decrease forward voltage of the lightemitting diode.

On the other hand, in a process of dicing light emitting diodes on awafer into individual light emitting diodes, an insulation layer exposedto a plane to be cut is likely to suffer from cracks. Such cracks canpropagate into the light emitting diode. Moreover, interlayerdelamination occurs due to cracks, thereby causing delamination of theinsulation layer from semiconductor layers. Accordingly, moisture andcontaminants can infiltrate the light emitting diode along an interfacebetween the insulation layer and a semiconductor layer, therebycontaminating the light emitting diode, and delamination force withrespect to layers in the light emitting diode can be reduced, therebycausing deterioration in reliability of the light emitting diode.

SUMMARY

Exemplary embodiments of the disclosed technology provide a lightemitting diode chip having an electrostatic discharge protectionfunction.

In addition, exemplary embodiments of the disclosed technology provide alight emitting diode which can be directly mounted on a printed circuitboard or the like using a solder paste by preventing diffusion of metalelements from the solder paste.

Further, exemplary embodiments of the disclosed technology provide alight emitting diode having improved current spreading performance.

Furthermore, exemplary embodiments of the disclosed technology provide alight emitting diode having improved light extraction efficiency byimproving reflectivity.

Furthermore, exemplary embodiments of the disclosed technology provide alight emitting diode a having low forward voltage.

Furthermore, exemplary embodiments of the disclosed technology provide alight emitting diode capable of simplifying a manufacturing process byreducing the use of photomasks, an LED module including the same, and amethod of fabricating the same.

Furthermore, exemplary embodiments of the disclosed technology provide alight emitting diode having improved reliability and luminous efficacyby preventing damage to the light emitting diode due to cracks.

Additional features of the disclosed technology will be set forth in thedescription which follows, and in part will become apparent from thedescription, or may be learned from practice of the disclosedtechnology.

In one aspect, a light emitting diode includes: a first conductive-typesemiconductor layer; a second conductive-type semiconductor layer; anactive layer interposed between the first conductive-type semiconductorlayer and the second conductive-type semiconductor layer; a firstelectrode pad region electrically connected to the first conductive-typesemiconductor layer; a second electrode pad region electricallyconnected to the second conductive-type semiconductor layer; and a sparkgap formed between a first leading end electrically connected to thefirst electrode pad region and a second leading end electricallyconnected to the second electrode pad region. The spark gap can achieveelectrostatic discharge protection of the light emitting diode.

In some implementations, the light emitting diode may further include anupper insulation layer covering the second conductive-type semiconductorlayer, the upper insulation layer including an opening that exposes thespark gap. As the spark gap is exposed to the outside, it is possible toprevent generation of static electricity by electrical sparks via air.

In some implementations, the light emitting diode may include a mesaplaced on the first conductive-type semiconductor layer, the mesaincluding the active layer and the second conductive-type semiconductorlayer, and the first electrode pad region may be electrically connectedto the first conductive-type semiconductor layer at a side of the mesa.

In some implementations, the light emitting diode may further include areflective electrode structure placed on the mesa; and a currentspreading layer covering the mesa and the first conductive-typesemiconductor layer, and having an opening that exposes the reflectiveelectrode structure, the current spreading layer being electricallyconnected to the first conductive-type semiconductor layer while beinginsulated from the reflective electrode structure and the mesa, whereinthe upper insulation layer covers the current spreading layer and thefirst leading end may be a portion of the current spreading layer.

In some implementations, the light emitting diode may further include ananti-diffusion reinforcing layer placed on the reflective electrodestructure in the opening of the current spreading layer, wherein thesecond leading end may be a portion of the anti-diffusion reinforcinglayer. In some implementations, the anti-diffusion reinforcing layer maybe formed of the same material as that of the current spreading layer.

In some implementations, the upper insulation layer may include a firstopening that exposes the current spreading layer to define the firstelectrode pad region, and a second opening that exposes theanti-diffusion reinforcing layer to define the second electrode padregion.

In some implementations, the light emitting diode may further include alower insulation layer placed between the mesa and the current spreadinglayer and insulating the current spreading layer from the mesa, thelower insulation layer having an opening placed in an upper region ofthe mesa and exposing the reflective electrode structure.

In some implementations, the spark gap may be placed between the firstelectrode pad region and the second electrode pad region. The spark gapgenerates electric sparks when static electricity of high voltage isapplied between the first electrode pad region and the second electrodepad region. To this end, a gap between the first leading end and thesecond leading end may be narrower than other portions. In someimplementations, the first leading end and the second leading end mayhave a semi-circular or angled shape and face each other.

In another aspect, a method of fabricating a light emitting diode isprovided to include: forming a first conductive-type semiconductorlayer, an active layer and a second conductive-type semiconductor layeron a substrate; patterning the second conductive-type semiconductorlayer and the active layer to form a mesa on the first conductive-typesemiconductor layer; and forming a first electrode pad regionelectrically connected to the first conductive-type semiconductor layerand a second electrode pad region electrically connected to the secondconductive-type semiconductor layer. Furthermore, the light emittingdiode has a spark gap defined between the first leading end electricallyconnected to the first electrode pad region and the second leading endelectrically connected to the second electrode pad region.

In some implementations, the method may further include: forming areflective electrode structure on the second conductive-typesemiconductor layer; and forming a current spreading layer covering themesa and the first conductive-type semiconductor layer, and having anopening exposing the reflective electrode structure, the currentspreading layer forming ohmic contact with the first conductive-typesemiconductor layer while being insulated from the mesa, wherein thefirst leading end is a portion of the current spreading layer.

The current spreading layer allows uniform spreading of current in thefirst conductive-type semiconductor layer. The first leading end may bea portion of the current spreading layer.

In some implementations, the method may further include forming ananti-diffusion reinforcing layer on the reflective electrode structure,the anti-diffusion reinforcing layer being formed together with thecurrent spreading layer, wherein the second leading end is a portion ofthe anti-diffusion reinforcing layer. Thus, the first and second leadingends can be formed together with the current spreading layer and theanti-diffusion reinforcing layer by the same process.

In some implementations, the method may further include forming an upperinsulation layer covering the current spreading layer, the upperinsulation layer having a first opening exposing the current spreadinglayer to define the first electrode pad region, and a second openingexposing the anti-diffusion reinforcing layer to define the secondelectrode pad region.

In some implementations, the upper insulation layer may further includean opening through which the first leading end and the second leadingend are exposed. The opening may be distant from the first and secondopenings.

In some implementations, the method may further include forming a lowerinsulation layer covering the mesa and the first conductive-typesemiconductor layer, before forming the current spreading layer, thelower insulation layer having openings that expose the reflectiveelectrode structure and the first conductive-type semiconductor layer.

In some implementations, the lower insulation layer may include asilicon oxide layer and the upper insulation layer may include a siliconnitride layer.

In some implementations, the method may further include forming ananti-Sn diffusion plating layer on the first electrode pad region andthe second electrode pad region using a plating technique.

In another aspect, a light emitting diode (LED) module is provided tocomprise: a printed circuit board; and a light emitting diode bonded toan upper side of the printed circuit board, the light emitting diodecomprising: a first conductive-type semiconductor layer; a mesa placedon the first conductive-type semiconductor layer and including an activelayer and a second conductive-type semiconductor layer; a reflectiveelectrode structure placed on the mesa; a current spreading layercovering the mesa and the first conductive-type semiconductor layer, andhaving an opening that exposes the reflective electrode structure, thecurrent spreading layer being electrically connected to the firstconductive-type semiconductor layer while being insulated from thereflective electrode structure and the mesa; and an upper insulationlayer covering the current spreading layer, the upper insulation layerhas a first opening exposing the current spreading layer to define thefirst electrode pad region, and a second opening exposing an exposedupper region of the reflective electrode structure to define the secondelectrode pad region, wherein the first electrode pad region and thesecond electrode pad region are bonded to corresponding pads on theprinted circuit boards via solder pastes, respectively.

Since the first and second electrode pad regions are respectivelydefined by the first and second openings of the upper insulation layer,there is no need for a separate photomask for forming the first andsecond electrode pads.

In some implementations, the light emitting diode may further include ananti-Sn diffusion plating layer formed on the first electrode pad regionand the second electrode pad region.

Unlike typical AuSn solders in the related art, the solder paste is amixture of a metal alloy and an organic material and is cured by heattreatment to provide a bonding function. Thus, metal elements such as Snin the solder paste are unlikely to diffuse, unlike metal elements inthe typical AuSn solders in the related art.

The anti-Sn diffusion plating layer can prevent the metal elements suchas Sn in the solder paste from diffusing into the light emitting diode.Furthermore, as the anti-Sn diffusion plating layer is formed by aplating technique such as electroless plating, there is no need for aseparate photomask for formation of the plating layer.

In some embodiments, the light emitting diode may further include ananti-diffusion reinforcing layer placed on the reflective electrodestructure in the opening of the current spreading layer, theanti-diffusion reinforcing layer being exposed through the secondopening of the upper insulation layer. The anti-diffusion reinforcinglayer can prevent metal elements such as Sn in the solder paste fromdiffusing to the reflective electrode structure in the light emittingdiode.

In some implementations, the anti-diffusion reinforcing layer may beformed of the same material as that of the current spreading layer.

Thus, the anti-diffusion reinforcing layer may be formed together withthe current spreading layer, and there is no need for a separatephotomask for formation of the anti-diffusion reinforcing layer.

In some implementations, the current spreading layer may include anohmic contact layer, a reflective metal layer, an anti-diffusion layer,and an anti-oxidation layer. In some implementations, the currentspreading layer may form ohmic contact with the first conductive-typesemiconductor layer through the ohmic contact layer. For example, theohmic contact layer may be formed of Ti, Cr, Ni, and the like.

The reflective metal layer reflects light incident on the currentspreading layer to increase reflectivity of the light emitting diode.The reflective metal layer may be formed of Al. In addition, theanti-diffusion layer prevents diffusion of metal elements and serves toprotect the reflective metal layer. For example, the anti-diffusionlayer can prevent diffusion of metal elements such as Sn in the solderpaste. In some implementations, the anti-diffusion layer may include Cr,Ti, Ni, Mo, TiW, or W or combinations thereof. Each of Mo, TiW and W maybe used to form a single layer. On the other hand, Cr, Ti, and Ni may beused to form a pair of layers.

In some implementations, the anti-diffusion layer may include at leasttwo pairs of Ti/Ni or Ti/Cr layers. In some implementations, theanti-oxidation layer is formed to prevent oxidation of theanti-diffusion layer and may include Au.

In some implementations, the current spreading layer may have areflectivity of 65% to 75%. Thus, the light emitting diode according tothis embodiment of the invention can provide optical reflection by thecurrent spreading layer in addition to optical reflection by thereflective electrode structure, whereby light traveling through asidewall of the mesa and the first conductive-type semiconductor layercan be reflected.

In some implementations, the current spreading layer may further includea bonding layer placed on the anti-oxidation layer. In someimplementations, the bonding layer may include Ti, Cr, Ni or Ta. Thebonding layer is used to enhance bonding strength between the currentspreading layer and the upper insulation layer.

In some implementations, the solder paste may adjoin the currentspreading layer and the anti-diffusion reinforcing layer. Alternatively,the solder paste may adjoin the anti-Sn diffusion plating layer formedon the current spreading layer and the anti-diffusion reinforcing layer.

In some implementations, the reflective electrode structure may includea reflective metal section; a capping metal section; and ananti-oxidation metal section, the reflective metal section having aslanted side surface such that an upper surface of the reflective metalsection has a narrower area than a lower surface thereof, and wherein astress relief layer is formed at an interface between the reflectivemetal section and the capping metal section. The stress relief layerrelieves stress due to a difference in coefficient of thermal expansionbetween the metal layers formed of different materials.

In some implementations, the mesa may include elongated branchesextending parallel to each other in one direction, and a connectingportion at which the branches are connected to each other, and theopening of the current spreading layer may be placed on the connectingportion.

In some implementations, the light emitting diode may further include alower insulation layer placed between the mesa and the current spreadinglayer and insulating the current spreading layer from the mesa, thelower insulation layer has an opening that is placed in an upper regionof the mesa and exposes the reflective electrode structure.

In some implementations, the opening of the current spreading layer mayhave a greater width than the opening of the lower insulation layer suchthat the opening of the lower insulation layer is completely exposedtherethrough. As a result, the current spreading layer can be insulatedfrom the reflective electrode structure.

In some implementations, the light emitting diode may further include ananti-diffusion reinforcing layer placed within the opening of thecurrent spreading layer and the opening of the lower insulation layer,and the anti-diffusion reinforcing layer may be exposed through thesecond opening of the upper insulation layer.

In some implementations, the lower insulation layer may include asilicon oxide layer and the upper insulation layer may include a siliconnitride layer. As the upper insulation layer is formed of siliconnitride, it is possible to prevent diffusion of metal elements from thesolder paste through the upper insulation layer.

In some implementations, the solder paste may include lead-free solderalloys, for example, Sn—Ag alloys, Sn—Bi alloys, Sn—Zn alloys, orSn—Ag—Cu alloys.

The light emitting diode may further include a substrate and awavelength conversion layer covering a lower surface of the substrate.The substrate may be a growth substrate for growing the semiconductorlayers. In addition, the wavelength conversion layer may cover the lowersurface and a side surface of the substrate.

In another aspect, a light emitting diode is provided to comprise: afirst conductive-type semiconductor layer; a mesa disposed on the firstconductive-type semiconductor layer and comprising an active layer and asecond conductive-type semiconductor layer; a reflective electrodestructure disposed on the mesa; a current spreading layer covering themesa and the first conductive-type semiconductor layer, and having anopening exposing the reflective electrode structure, the currentspreading layer being electrically connected to the firstconductive-type semiconductor layer while being insulated from thereflective electrode structure and the mesa; and an upper insulationlayer covering the current spreading layer, the upper insulation layerhaving a first opening exposing the current spreading layer to define afirst electrode pad region, and a second opening exposing an exposedupper region of the reflective electrode structure to define the secondelectrode pad region.

In some implementations, the light emitting diode further comprises: ananti-diffusion reinforcing layer disposed on the reflective electrodestructure in the opening of the current spreading layer, wherein theanti-diffusion reinforcing layer is exposed through the second openingof the upper insulation layer, and is formed of the same material asthat of the current spreading layer. In some implementations, the lightemitting diode further comprises: anti-solder diffusion layers formed inthe first opening and the second opening. In some implementations, thecurrent spreading layer comprises an ohmic contact layer, a reflectivemetal layer, an anti-diffusion layer, and an anti-oxidation layer.

In another aspect, a method of fabricating a light emitting diode isprovided. The method may include: forming a first conductive-typesemiconductor layer, an active layer and a second conductive-typesemiconductor layer on a substrate; patterning the secondconductive-type semiconductor layer and the active layer to form a mesaon the first conductive-type semiconductor layer while forming areflective electrode structure on the mesa to form ohmic contact withthe mesa; forming a current spreading layer covering the mesa and thefirst conductive-type semiconductor layer, and having an opening thatexposes the reflective electrode structure, the current spreading layerforming ohmic contact with the first conductive-type semiconductor layerwhile being insulated from the mesa; and forming an upper insulationlayer covering the current spreading layer, the upper insulation layerhaving a first opening exposing the current spreading layer to define afirst electrode pad region, and a second opening exposing an exposedupper region of the reflective electrode structure to define the secondelectrode pad region.

In the fabrication method, since there is no need for formation ofelectrode pads on the upper insulation layer, it is possible to reducethe number of photomasks for fabrication of the light emitting diode.

In some implementations, the method may further include forming ananti-diffusion reinforcing layer on the reflective electrode structure,wherein the anti-diffusion reinforcing layer can be formed together withthe current spreading layer, and the second opening of the upperinsulation layer can expose the anti-diffusion reinforcing layer.Accordingly, the reflective electrode structure can be concealed andprotected by the anti-diffusion reinforcing layer and the upperinsulation layer.

In some implementations, the method may further include forming a lowerinsulation layer covering the mesa and the first conductive-typesemiconductor layer, before forming the current spreading layer;dividing the lower insulation layer and the first conductive-typesemiconductor layer into chip regions by laser scribing; and patterningthe lower insulation layer to form openings exposing the firstconductive-type semiconductor layer and an opening exposing thereflective electrode structure.

Since a chip isolation region is formed using laser scribing, there isno need for use of a photomask. In addition, since laser scribing isperformed after formation of the lower insulation layer, particlesformed in the laser scribing process can be easily removed by cleaningthe lower insulation layer, whereby the light emitting diode can beprevented from being contaminated by the particles.

In some implementations, the lower insulation layer may include asilicon oxide layer and the upper insulation layer may include a siliconnitride layer.

In some implementations, the method may further include forming ananti-Sn diffusion plating layer on the first electrode pad region andthe second electrode pad region using a plating technique. The platinglayer may be formed by electroless plating such as ENIG (electrolessnickel immersion gold) and the like.

In some implementations, the substrate may be partially removed to havea small thickness by grinding and/or lapping. Then, the substrate isseparated from the chip isolation region formed by laser scribing,thereby providing final individual chips separated from each other.Next, a wavelength conversion layer may be coated onto the lightemitting diode chips, and the light emitting diode having the wavelengthconversion layer is mounted on a printed circuit board via a solderpaste, thereby providing an LED module.

The wavelength conversion layer may be formed by coating aphosphor-containing resin, followed by curing the resin. Alternatively,the wavelength conversion layer may be formed by spraying phosphorpowder onto the light emitting diode chip using an aerosol apparatus.

In another aspect, a light emitting diode is provided to include: afirst conductive-type semiconductor layer; a mesa including a secondconductive-type semiconductor layer disposed over the firstconductive-type semiconductor layer and an active layer interposedbetween the second conductive-type semiconductor layer and the firstconductive-type semiconductor layer; and a first electrode disposed overthe mesa, wherein the first conductive-type semiconductor layer includesa first contact region disposed around the mesa along an outer peripheryof the first conductive-type semiconductor layer; and a second contactregion at least partially surrounded by the mesa, the first electrode iselectrically connected to at least a portion of the first contact regionand at least a portion of the second contact region, and a linewidth ofan adjoining region between the first contact region and the firstelectrode is greater than the linewidth of an adjoining region betweenthe second contact region and the first electrode. With the structurewherein a contact area between the first electrode and the firstconductive-type semiconductor layer through the first contact region isrelatively increased as compared with a contact area between the firstelectrode and the first conductive-type semiconductor layer through thesecond contact region, the light emitting diode can have a reducedforward voltage (Vf). Furthermore, the light emitting diode can haveimproved luminous efficacy by more effectively spreading electriccurrent in the horizontal direction.

In some implementations, the second contact region may be electricallyconnected to the first contact region. With this structure, the lightemitting diode can have improved luminous efficacy by more effectivelyspreading electric current in the horizontal direction.

In some implementations, a length of the second contact region in amajor axis direction may be 0.5 times or more the length of one side ofthe light emitting diode. With this structure, a contact area betweenthe first electrode and the first conductive-type semiconductor layercan be increased, such that electric current flowing from the firstelectrode to the first conductive-type semiconductor layer can be moreeffectively dispersed, thereby further reducing forward voltage.

In some implementations, the linewidth of the adjoining region betweenthe first contact region and the first electrode may be greater than 10μm and the linewidth of the adjoining region between the second contactregion and the first electrode may be 10 μm or less.

In some implementations, the light emitting diode may further include afirst insulation layer interposed between the first electrode and themesa, and the first insulation layer may partially expose the firstcontact region and the second contact region.

In some implementations, the first insulation layer may be restrictivelydisposed closer to the mesa than the adjoining region between the firstcontact region and the first electrode. With this structure, it ispossible to increase the contact area between the first electrode andthe first conductive-type semiconductor layer without decreasing a lightemitting area. Furthermore, in a process of dicing light emitting diodesof a wafer into individual light emitting diodes, it is possible toprevent the first insulation layer disposed along the outer periphery ofthe first conductive-type semiconductor layer from suffering fromcracking. Accordingly, it is possible to prevent delamination force ofthe first electrode or a second insulation layer described below fromweakening due to infiltration of moisture or contaminants through thecracks, and to prevent contamination of the first electrode, therebyimproving reliability of the light emitting diode.

In some implementations, the first electrode may contact the firstcontact region and the second contact region that are exposed throughthe first insulation layer while exposing an outer periphery of thefirst contact region.

In some implementations, a portion of the first conductive-typesemiconductor layer not disposed under the first insulation layer mayhave a smaller thickness than a portion of the first conductive-typesemiconductor layer disposed under the first insulation layer. A portionof an upper surface of the first conductive-type semiconductor layer isremoved by etching, so that inert particles causing deterioration inconductivity and adhesion can be removed.

In some implementations, the first insulation layer disposed on an uppersurface of the second conductive-type semiconductor layer may have thesame thickness as the first insulation layer disposed on the uppersurface of the first conductive-type semiconductor layer. Accordingly,it is possible to prevent infiltration of external contaminants into alateral side of the mesa.

In some implementations, the light emitting diode may further include asecond insulation layer covering the first electrode and the secondcontact region exposed through the first electrode.

In some implementations, the first electrode includes a plurality oflayers, and an upper portion of the first electrode contacting thesecond insulation layer may include a Ti layer. With this structure, thelight emitting diode has improved reliability through improvement inbonding strength between the first electrode and the second insulationlayer.

In some implementations, the second insulation layer may include anopening exposing the first electrode, and an upper portion of the firstelectrode exposed through the opening of the second insulation layer mayinclude an Au layer.

In some implementations, the light emitting diode may further include afirst pad contacting the first electrode, wherein the first pad maycontact the exposed Au layer. With this structure, the light emittingdiode can exhibit improved bonding strength between the first pad andthe first electrode and can reduce resistance.

In some implementations, the light emitting diode may further include asecond electrode disposed on the second conductive-type semiconductorlayer and electrically connected to the second conductive-typesemiconductor layer, wherein the second electrode may be insulated fromthe first electrode by the first insulation layer.

In some implementations, a portion of the first insulation layerdisposed on an upper surface of the second electrode may have a smallerthickness than a portion of the first insulation layer disposed on theupper surface of the second conductive-type semiconductor layer.

In some implementations, the second electrode includes a plurality oflayers, and an upper portion of the second electrode contacting thefirst insulation layer may be a Ti layer. With this structure, the lightemitting diode has improved bonding strength between the secondelectrode and the first insulation layer, thereby providing improvedreliability.

In some implementations, the first insulation layer may include anopening exposing the second electrode, and an upper portion of thesecond electrode exposed through the opening of the first insulationlayer may include an Au layer.

In some implementations, the light emitting diode may further include asecond pad contacting the second electrode, and the second pad maycontact the exposed Au layer. With this structure, the light emittingdiode can exhibit improved bonding strength between the second pad andthe second electrode and can reduce resistance.

In some implementations, the light emitting diode may further include agrowth substrate disposed under the first conductive-type semiconductorlayer.

In some implementations, the second insulation layer may cover anoverall region of a side surface of the first conductive-typesemiconductor layer and a portion of a side surface of the growthsubstrate. With this structure, the light emitting diode can protect thefirst conductive-type semiconductor layer from external moisture orimpact, and can prevent an interface between the growth substrate andthe first conductive-type semiconductor layer from splitting, therebyimproving reliability.

In some implementations, the growth substrate may include at least onereformed region having a stripe shape and extending from at least oneside surface of the growth substrate in a horizontal direction thereof.With this structure, the light emitting diode can have improvedefficiency in extraction of light generated from the active layer.

In some implementations, the second insulation layer may be separatedfrom the outer periphery of the first conductive-type semiconductorlayer by a predetermined distance. Accordingly, it is possible tominimize damage to the second insulation layer in a process of dividingthe wafer into individual light emitting diodes.

In some implementations, the mesa may include a plurality of protrusionsprotruding towards one side of the first conductive-type semiconductorlayer; and a plurality of protrusions protruding towards the other sideof the first conductive-type semiconductor layer. With this structure,not only in a region adjacent the one side of the first conductive-typesemiconductor layer but also in a region adjacent the other side of thefirst conductive-type semiconductor layer, the light emitting diode canachieve efficient current flow between the second electrode disposed onthe protrusions and the first electrode disposed on the second contactregion. Accordingly, the region adjacent the other side of the firstconductive-type semiconductor layer has improved luminous efficacy.

According to embodiments of the disclosed technology, it is possible toprotect light emitting diodes from static electricity by forming a sparkgap. In addition, some implementations of the disclosed technologyprovide a light emitting diode, which can prevent diffusion of metalelements from a solder paste, and a method for fabricating the same.Further, some implementations of the disclosed technology provide alight emitting diode having improved current spreading performance, forexample, a flip-chip type light emitting diode having improved currentspreading performance. Furthermore, the light emitting diodes accordingto some implementations of the disclosed technology have improvedreflectivity by forming a current spreading layer, thereby providingimproved light extraction efficiency. Furthermore, the light emittingdiodes according to some implementations of the disclosed technology canomit a photolithography process for formation of electrode pads, and canreduce the number of photomasks by forming a chip isolation region usinga laser scribing technique. Furthermore, electric current flowing fromthe first electrode to the first conductive-type semiconductor layer canefficiently spread, thereby reducing a forward voltage. Furthermore, thefirst electrode can be prevented from being contaminated due to cracksin the first insulation layer, thereby improving reliability of thelight emitting diode.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view of an exemplary LED module inaccordance with an embodiment of the disclosed technology.

FIG. 2(a) to FIG. 10 are views illustrating an exemplary method offabricating a light emitting diode in accordance with an embodiment ofthe disclosed technology, and in each of FIG. 2 to FIG. 9, (a) is a planview, (b) is a cross-sectional view taken along line A-A, and (c) is across-sectional view taken along line B-B.

FIG. 11(a) to FIG. 14(c) are views illustrating an exemplary method offabricating a light emitting diode in accordance with an embodiment ofthe disclosed technology, and in each of FIG. 11 to FIG. 14, (a) is aplan view, (b) is a cross-sectional view taken along line A-A, and (c)is a cross-sectional view taken along line B-B.

FIG. 15 is a plan view of a light emitting diode in accordance with anembodiment of the disclosed technology.

FIG. 16 is a cross-sectional view taken along line A-B-B′-A′ of FIG. 15.

FIG. 17 is a cross-sectional view taken along line C-C′ of FIG. 15.

FIG. 18 is an enlarged sectional view of part I₁ of FIG. 16.

FIG. 19 is a sectional view of a light emitting diode in accordance withan embodiment of the disclosed technology and a circuit member on whichthe light emitting diode is mounted.

FIG. 20 is an enlarged sectional view of part I₂ of FIG. 19.

FIG. 21 is an enlarged sectional view of part I₃ of FIG. 20.

FIG. 22 is a sectional view illustrating a structure wherein the lightemitting diode in accordance with an embodiment of the disclosedtechnology is mounted on a circuit member.

FIG. 23 is a plan view of a light emitting diode in accordance with anembodiment of the disclosed technology.

FIG. 24 is a cross-sectional view taken along line A-B-B′-A′ of FIG. 23.

FIG. 25 is a side view of the light emitting diode of FIG. 23.

FIG. 26 is a plan view of a light emitting diode in accordance with anembodiment of the disclosed technology.

FIG. 27 is a cross-sectional view taken along line A-B-B′-A′ of FIG. 26.

FIG. 28 is a plan view of a light emitting diode in accordance with anembodiment of the disclosed technology.

FIG. 29 is a cross-sectional view taken along line A-A′ of FIG. 28.

FIG. 30 is a cross-sectional view taken along line B-B′ of FIG. 28.

FIG. 31 is an exploded perspective view of an exemplary lightingapparatus to which a light emitting diode in accordance with anembodiment of the disclosed technology is applied.

FIG. 32 is a sectional view of an exemplary display to which a lightemitting diode in accordance with an embodiment of the disclosedtechnology is applied.

FIG. 33 is a sectional view of an exemplary display to which a lightemitting diode in accordance with an embodiment of the disclosedtechnology is applied.

FIG. 34 is a sectional view of an exemplary headlight to which a lightemitting diode in accordance with an embodiment of the disclosedtechnology is applied.

DETAILED DESCRIPTION

In the related art, the light emitting diode employs linear extensionlegs which have high resistance, which results in imposing some limit oncurrent spreading. Moreover, since the reflective electrode is placedonly on the P-type semiconductor layer, a substantial amount of light isabsorbed by the electrode pads and extension legs while not beingreflected by the reflective electrode and thus, substantial light lossis caused. When used in a final product, the light emitting diode isprovided by an LED module. The LED module generally includes a printedcircuit board and an LED package mounted on the printed circuit board,in which the light emitting diode is mounted in chip form within the LEDpackage. A typical LED chip is packaged after being mounted on asub-mount, a lead frame or a lead electrode by silver pastes or AuSnsolders. Then, the LED package is mounted on the printed circuit boardby solder pastes. As a result, pads on the LED chip are distant from thesolder pastes, and bonded to the printed circuit board by a relativelystable bonding material such as silver pastes, AuSn, and the like.

Recently, various attempts have been made to fabricate an LED module bydirectly bonding electrode pads of a light emitting diode to a printedcircuit board using solder pastes. For example, an LED module can befabricated by directly mounting an LED chip on a printed circuit boardinstead of packaging the LED chip. Otherwise, an LED module can befabricated by mounting a so-called wafer level LED package on a printedcircuit board. In these LED modules, since the electrode pads directlyadjoin the solder pastes, metal elements such as tin (Sn) diffuse fromthe solder pastes into the light emitting diode through the pads andcause short circuit in the light emitting diode and device failure.

GaN-based compound semiconductors are formed by epitaxial growth on asapphire substrate, the crystal structure and lattice parameter of whichare similar to those of the semiconductors, in order to reduce crystaldefects. However, the epitaxial layers grown on the sapphire substratecontain many crystal defects such as V-pits, threading dislocations, andthe like. When high voltage static electricity is applied to theepitaxial layers, current is concentrated at crystal defects in theepitaxial layers, causing diode breakdown. Thus, with respect toelectrostatic discharge or electrical fast transient (EFT), which is aspark generated in a switch, and lightning surge in air, securingreliability of LEDs becomes important.

Generally, in packaging of a light emitting diode, a Zener diode ismounted together with the light emitting diode to prevent electrostaticdischarge. However, the Zener diode is expensive and a process ofmounting the Zener diode increases the number of processes for packagingthe light emitting diode and manufacturing costs. Moreover, since theZener diode is placed near the light emitting diode in the LED package,the LED package has deteriorated luminous efficacy due to absorption oflight by the Zener diode and deteriorated LED package yield.

Hereinafter, exemplary embodiments of the disclosed technology will bedescribed in detail with reference to the accompanying drawings. Itshould be understood that the following embodiments are provided as someexamples of the disclosed technology to facilitate understanding of thedisclosed technology. Thus, it should be understood that the disclosedtechnology is not limited to the following embodiments and may beembodied in different ways. In addition, in the drawings, the width,length and thickness of components may be exaggerated for convenience.Further, it should be noted that the drawings are not to precise scale.Like components will be denoted by like reference numerals throughoutthe specification.

FIG. 1 is a schematic sectional view of an LED module in accordance withone embodiment of the disclosed technology.

Referring to FIG. 1, an LED module according to an exemplary embodimentof the disclosed technology includes a printed circuit board 51 havingpads 53 a and 53 b and a light emitting diode 100 bonded to the printedcircuit board 51 via solder pastes 55.

The printed circuit board has a printed circuit thereon, and anysubstrate capable of providing an LED module can be used as the printedcircuit board without limitation.

Conventionally, a light emitting diode is mounted on a substrate havinga lead frame or lead electrodes formed thereon, and a light emittingdiode package including such a light emitting diode is mounted on aprinted circuit board. According to some implementations, the lightemitting diode 100 is directly mounted on the printed circuit board 51via the solder pastes 55.

The light emitting diode 100 may include a flip-chip type light emittingdiode and be mounted upside down on the printed circuit board. To thisend, the light emitting diode 100 has a first electrode pad region 43 aand a second electrode pad region 43 b. The first and second electrodepad regions 43 a and 43 b may be formed in a recess shape on one surfaceof the light emitting diode 100.

On the other hand, a lower surface of the light emitting diode 100, forexample, a surface of the light emitting diode opposite the first andsecond electrode pad regions 43 a and 43 b, may be covered with awavelength conversion layer 45. The wavelength conversion layer 45 maycover not only the lower surface of the light emitting diode 100 butalso side surfaces of the light emitting diode 100.

In FIG. 1, the light emitting diode is schematically shown forconvenience of description. The structure and respective components ofthe light emitting diode will be more clearly understood in thefollowing description of a method of fabricating the light emittingdiode. Furthermore, it should be noted that light emitting diodesaccording to embodiments of the disclosed technology are not limited tothe structure in which the light emitting diode is directly mounted onthe printed circuit board.

FIG. 2(a) to FIG. 10 are views illustrating a method of fabricating alight emitting diode in accordance with an exemplary embodiment of thedisclosed technology. In each feature, (a) is a plan view, (b) is across-sectional view taken along line A-A, and (c) is a cross-sectionalview taken along line B-B.

First, referring to FIGS. 2(a) to 2(c), a first conductive-typesemiconductor layer 23, an active layer 25 and a second conductive-typesemiconductor layer 27 are grown on a substrate 21. The substrate 100enables the growth of a GaN-based semiconductor layer, and may include,for example, a sapphire substrate, a silicon carbide substrate, a GaNsubstrate, or a spinel substrate, and the like. In some implementations,the substrate may be or include a patterned substrate such as apatterned sapphire substrate.

For example, the first conductive-type semiconductor layer may includean n-type gallium nitride-based layer and the second conductive-typesemiconductor layer 27 may include a p-type gallium nitride-based layer.In addition, the active layer 25 may have a single quantum wellstructure or a multi-quantum well structure, and may include well layersand barrier layers. In addition, the composition of the well layers maybe determined according to the wavelength of light and may include, forexample, AlGaN, GaN or InGaN.

On the other hand, a pre-oxidation layer 29 may be formed on the secondconductive-type semiconductor layer 27. The pre-oxidation layer 29 maybe formed of or include, for example, SiO₂ by chemical vapor deposition.

Then, a photoresist pattern 30 is formed. The photoresist pattern 30 ispatterned to have openings 30 a. As shown in FIG. 2(a) and FIG. 2(b),the openings 30 a are formed such that an inlet of each opening has anarrower width than a bottom of the opening. The photoresist pattern 30having the openings 30 a of this structure can be easily formed using anegative type photoresist.

Referring to FIGS. 3(a) to 3(c), the pre-oxidation layer 29 is etchedusing the photoresist pattern 30 as an etching mask. The pre-oxidationlayer 29 may be etched by wet etching. As a result, the pre-oxidationlayer 29 in the openings 30 a of the photoresist pattern 30 is etched toform openings 29 a of the pre-oxidation layer 29, which expose thesecond conductive-type semiconductor layer 27. The bottom portions ofthe openings 29 a are generally similar or greater than the bottomportions of the openings 30 a of the photoresist pattern 30.

Referring to FIG. 4, a reflective electrode structure 35 is formed by alift-off technology. The reflective electrode structure 35 may include areflective metal section 31, a capping metal section 32 and ananti-oxidation metal section 33. The reflective metal section 31includes a reflective layer, and a stress relief layer may be furtherformed between the reflective metal section 31 and the capping metalsection 32. The stress relief layer relieves stress due to difference incoefficient of thermal expansion between the reflective metal section 31and the capping metal section 32.

The reflective metal section 31 may be formed of or include, forexample, Ni/Ag/Ni/Au, and may have an overall thickness of about 1600 Å.As shown, the reflective metal section 31 is formed to have a slantedside surface, for example, such that the bottom of the reflective metalsection has a relatively wide area. Such a reflective metal section 31may be formed by e-beam evaporation.

The capping metal section 32 covers upper and side surfaces of thereflective metal section 31 to protect the reflective metal section 31.The capping metal section 32 may be formed by sputtering or by e-beamevaporation, for example, planetary e-beam evaporation, in which vacuumdeposition is performed while rotating the substrate 21 in a slantedstate. The capping metal section 32 may include Ni, Pt, Ti, or Cr, andmay be formed by depositing, for example, about five pairs of Ni/Ptlayers or about five pairs of Ni/Ti layers. Alternatively, the cappingmetal section 32 may include TiW, W, or Mo.

A material for the stress relief layer may be selected in various waysdepending upon metal components of the reflective layer and the cappingmetal section 32. For example, when the reflective layer is composed ofor includes Al or Al-alloys and the capping metal section 32 is composedof or includes W, TiW or Mo, the stress relief layer may be or include asingle layer of Ag, Cu, Ni, Pt, Ti, Rh, Pd or Cr, or a composite layerof Cu, Ni, Pt, Ti, Rh, Pd or Au. In addition, when the reflective layeris composed of or includes Al or Al-alloys and the capping metal section32 is composed of or includes Cr, Pt, Rh, Pd or Ni, the stress relieflayer may be or include a single layer of Ag or Cu, or a composite layerof Ni, Au, Cu or Ag.

In addition, when the reflective layer is composed of or includes Ag orAg-alloys and the capping metal section 32 is composed of or includes W,TiW or Mo, the stress relief layer may be or include a single layer ofCu, Ni, Pt, Ti, Rh, Pd or Cr, or a composite layer of Cu, Ni, Pt, Ti,Rh, Pd, Cr or Au. Further, when the reflective layer is composed of orincludes Ag or Ag-alloys and the capping metal section 32 is composed ofor includes Cr or Ni, the stress relief layer may be or include a singlelayer of Cu, Cr, Rh, Pd, TiW or Ti, or a composite layer of Ni, Au orCu.

Further, the anti-oxidation metal section 33 includes Au in order toprevent oxidation of the capping metal section 32, and may be formed ofor include, for example, Au/Ni or Au/Ti. Since Ti secures adhesion of anoxide layer such as SiO₂, in some implementations, Ti can be used. Theanti-oxidation metal section 33 may also be formed by sputtering or bye-beam evaporation, for example, planetary e-beam evaporation, in whichvacuum deposition is performed while rotating the substrate 21 in aslanted state.

The photoresist pattern 30 is removed after deposition of the reflectiveelectrode structure 35, whereby the reflective electrode structure 35remains on the second conductive-type semiconductor layer 27, as shownin FIG. 4.

The reflective electrode structure 35 may include branches 35 b and aconnecting portion 35 a, as shown in FIG. 4. The branches 35 b may havean elongated shape and be parallel to each other. The connecting portion35 a connects the branches 35 b to each other. However, it should beunderstood that the reflective electrode structure 35 is not limited toa particular shape and may be modified into various shapes.

Referring to FIG. 5, a mesa M is formed on the first conductive-typesemiconductor layer 21. The mesa M includes the active layer 25 and thesecond conductive-type semiconductor layer 27. The active layer 25 isplaced between the first conductive-type semiconductor layer 23 and thesecond conductive-type semiconductor layer 27. The reflective electrodestructure 35 is placed on the mesa M.

The mesa M is formed by patterning the second conductive-typesemiconductor layer 27 and the active layer 25 so as to expose the firstconductive-type semiconductor layer 23. The mesa M may be formed to havea slanted side surface by photoresist reflow technology or the like. Theslanted profile of the side surface of the mesa M enhances extractionefficiency of light generated in the active layer 25.

As shown, the mesa M may include elongated branches Mb extendingparallel to each other in one direction and a connection portion Maconnecting the branches to each other. With such configuration of themesa, the light emitting diode can permit uniform spreading of electriccurrent in the first conductive-type semiconductor layer 23. Here, itshould be understood that the mesa M is not limited to a particularshape and may be modified into various shapes. On the other hand, thereflective electrode structure 35 covers most of the upper surface ofthe mesa M and generally has the same shape as the shape of the mesa Min plan view.

While the second conductive-type semiconductor layer 27 and the activelayer 25 are subjected to etching, the pre-oxidation layer 29 remainingon these layers is also partially removed by etching. On the other hand,although the pre-oxidation layer 29 can remain near an edge of thereflective electrode structure 35 on each of the mesa M, the remainingpre-oxidation layer 29 can also be removed by wet etching and the like.Alternatively, the pre-oxidation layer 29 may be removed beforeformation of the mesa M.

Referring to FIG. 6, after the mesa M is formed, a lower insulationlayer 37 is formed to cover the mesa M and the first conductive-typesemiconductor layer. The lower insulation layer 37 may be formed of orinclude an oxide layer such as SiO₂ and the like, a nitride layer suchas SiNx and the like, or an insulation layer of MgF₂ by chemical vapordeposition (CVD) and the like. The lower insulation layer 37 may be asingle layer or multiple layers. In addition, the lower insulation layer37 may be or include a distributed Bragg reflector (DBR) in which lowrefractive index material layers and high refractive index materiallayers are alternately stacked one above another. For example, aninsulating reflective layer having high reflectivity may be formed bystacking dielectric layers such as SiO₂/TiO₂, or SiO₂/Nb₂O₅, and thelike.

Then, a chip isolation region 23 h is formed by laser scribing to dividethe lower insulation layer 37 and the first conductive-typesemiconductor layer 23 into chip units. Grooves may be formed on theupper surface of the substrate 21 by laser scribing. As a result, thesubstrate 21 is exposed near an edge of the first conductive-typesemiconductor layer 23.

Since the first conductive-type semiconductor layer 23 is divided intochip units by laser scribing, it is possible to omit a separatephotomask for an isolation process. However, it should be understoodthat the disclosed technology is not limited to the isolation processusing laser scribing. For example, the first conductive-typesemiconductor layer 23 may be divided into chip units before or afterformation of the lower insulation layer 37 using a typicalphotolithography and etching technique.

As shown in FIG. 6, the mesa M may be formed to be placed only inside anupper region of the first conductive-type semiconductor layer 23. Forexample, the mesa M may be placed in an island shape on the upper regionof the first conductive-type semiconductor layer 23.

Next, referring to FIG. 7, the lower insulation layer 37 is subjected topatterning to form openings 37 a and 37 b in predetermined regions toallow electrical connection to the first conductive-type semiconductorlayer 23 and the second conductive-type semiconductor layer 27. Forexample, the lower insulation layer 37 may have openings 37 b whichexpose the first conductive-type semiconductor layer 23, and openings 37a which expose the reflective electrode structure 35.

The openings 37 a are placed only in upper regions of the mesas M, forexample, on the connecting portions of the mesas M. The openings 37 bmay be placed in regions between the branches Mb of the mesas M and nearthe edge of the substrate 21, and may have an elongated shape extendingalong the branches Mb of the mesas M.

Referring to FIG. 8, a current spreading layer 39 is formed on the lowerinsulation layer 37. The current spreading layer 39 covers the mesa Mand the first conductive-type semiconductor layer 23. In addition, thecurrent spreading layer 39 has an opening 39 a placed in the upperregion of the mesa M and exposing the reflective electrode structure 35.The current spreading layer 39 may form ohmic contact with the firstconductive-type semiconductor layer 23 through the opening 37 b of thelower insulation layer 37. The current spreading layer 39 is insulatedfrom the mesa M and the reflective electrodes 35 by the lower insulationlayer 37.

The opening 39 a of the current spreading layer 39 has a greater areathan the opening 37 a of the lower insulation layer 37 to prevent thecurrent spreading layer 39 from being connected to the reflectiveelectrode structures 35. Thus, the opening 39 a has sidewalls placed onthe lower insulation layer 37.

The current spreading layer 39 is formed on an overall upper region ofthe substrate 21 excluding the openings 39 a. Thus, electric current canbe easily dispersed through the current spreading layer 39.

The current spreading layer 39 may include an ohmic contact layer, areflective metal layer, an anti-diffusion layer, and an anti-oxidationlayer. The current spreading layer can form ohmic contact with the firstconductive-type semiconductor layer through the ohmic contact layer. Forexample, the ohmic contact layer may be formed of or include Ti, Cr, orNi, and the like. The reflective metal layer increases reflectivity ofthe light emitting diode by reflecting incident light entering thecurrent spreading layer. The reflective metal layer may be formed of orinclude Al. In addition, the anti-diffusion layer protects thereflective metal layer by preventing diffusion of metal elements. Forexample, the anti-diffusion layer can prevent diffusion of metalelements such as Sn within a solder paste. The anti-diffusion layer maybe composed of or include Cr, Ti, Ni, Mo, TiW, or W or combinationsthereof. The anti-diffusion layer may be a single layer including Mo,TiW or W. Alternatively, the anti-diffusion layer may include a pair ofCr, Ti or Ni layers. For example, the anti-diffusion layer may includeat least two pairs of Ti/Ni or Ti/Cr layers. The anti-oxidation layer isformed to prevent oxidation of the anti-diffusion layer and may includeAu.

The current spreading layer may have a reflectivity of 65% to 75%.Accordingly, the light emitting diode according to this embodiment canprovide optical reflection by the current spreading layer in addition tooptical reflection by the reflective electrode structure, whereby lighttraveling through the sidewall of the mesa and the first conductive-typesemiconductor layer can be reflected.

The current spreading layer may further include a bonding layer placedon the anti-oxidation layer. The bonding layer may include Ti, Cr, Ni orTa. The bonding layer is used to enhance bonding strength between thecurrent spreading layer and the upper insulation layer, and may beomitted.

For example, the current spreading layer 39 may have a multi-layerstructure including Cr/Al/Ni/Ti/Ni/Ti/Au/Ti.

While the current spreading layer 39 is formed, an anti-diffusionreinforcing layer 40 is formed on the reflective electrode structure 35.The anti-diffusion reinforcing layer 40 and the current spreading layer39 may be formed of or include the same material by the same process.The anti-diffusion reinforcing layer 40 is separated from the currentspreading layer 39. The anti-diffusion reinforcing layer 40 is placedwithin the opening 39 a of the current spreading layer 39.

The anti-diffusion reinforcing layer 40 has a leading end 40 a extendingtherefrom, and the current spreading layer 39 has a leading end 39 bfacing the leading end 40 a. The leading end 40 a may be placed on thelower insulation layer 37 outside the opening 37 a of the lowerinsulation layer 37. However, it should be understood that the disclosedtechnology is not limited thereto. Alternatively, the opening 37 a ofthe lower insulation layer 37 may have a similar shape to the shape ofthe leading end 40 a, and the leading end 40 a may be placed within theopening 40 a of the lower insulation layer 37.

The leading end 39 a of the current spreading layer 39 is placed on thelower insulation layer 37 and is separated from the leading end 40 a.The leading end 39 b and the leading end 40 a define a spark gaptherebetween. As a result, these leading ends 39 b and 40 a may beplaced closer than other portions or may have an angled shape in orderto allow generation of an electric spark between the leading ends 39 band 40 a when high voltage static electricity is applied to a gapbetween the current spreading layer 39 and the anti-diffusionreinforcing layer 40. For example, as shown in FIG. 8, the leading ends39 b and 40 a may have a semi-circular shape or an angled shape and maybe disposed to face each other.

Referring to FIG. 9, an upper insulation layer 41 is formed on thecurrent spreading layer 39. The upper insulation layer 41 has an opening41 a which exposes the current spreading layer 39 to define a firstelectrode pad region 43 a, and an opening 41 b which exposes thereflective electrode structure 35 to define a second electrode padregion 43 a. The opening 41 a may have an elongated shape perpendicularto the branches Mb of the mesa M. The opening 41 b of the upperinsulation layer 41 has a narrower area than the opening 39 a of thecurrent spreading layer 39 and thus the upper insulation layer 41 cancover the sidewall of the opening 39 a.

When the anti-diffusion reinforcing layer 40 is formed on the reflectiveelectrode structure 35, the opening 41 b exposes the anti-diffusionreinforcing layer 40. In this case, the reflective electrode structure35 can be concealed or sealed by the upper insulation layer 41 and theanti-diffusion reinforcing layer 40. Furthermore, the upper insulationlayer 41 has an opening 41 c which exposes at least part of the leadingend 39 b and the leading end 40 a. With this configuration, the sparkgap between the leading end 39 b and the leading end 40 a is exposed,thereby allowing generation of electrostatic discharge by an electricalspark through air.

Further, the upper insulation layer 41 may be formed on the chipisolation region 23 h to cover the side surface of the firstconductive-type semiconductor layer 23. With this configuration, it ispossible to prevent penetration of moisture and the like through upperand lower interfaces of the first conductive-type semiconductor layer.

The upper insulation layer 41 may be formed of or include a siliconnitride layer to prevent diffusion of metal elements from solder pastes,and may have a thickness of 1 m to 2 m. When the thickness of the upperinsulation layer is less than 1 m, it is difficult to prevent diffusionof metal the elements from the solder pastes.

Optionally, an anti-Sn diffusion plating layer (not shown) may beadditionally formed on the first electrode pad region 43 a and thesecond electrode pad region 43 b by electroless plating such as ENIG(electroless nickel immersion gold) and the like.

The first electrode pad region 43 a is electrically connected to thefirst conductive-type semiconductor layer 23 through the currentspreading layer 39, and the second electrode pad region 43 b iselectrically connected to the second conductive-type semiconductor layer27 through the anti-diffusion reinforcing layer 40 and the reflectiveelectrode structure 35.

The first electrode pad region 43 a and the second electrode pad region43 b are used to mount the light emitting diode on a printed circuitboard and the like via solder pastes. Thus, in order to prevent shortcircuit between the first electrode pad region 43 a and the secondelectrode pad region 43 b by the solder pastes, electrode pads may beseparated by a distance of about 300 m or more from each other.

Then, the substrate 21 may be removed to have a small thickness bypartially grinding and/or lapping a lower surface of the substrate 21.Then, the substrate 21 is divided into individual chip units, therebyproviding divided light emitting diode chips. Here, the substrate 21 maybe divided at the chip isolation region 23 h formed by laser scribingand thus there is no need for additional laser scribing for division ofchips.

The substrate 21 may be removed from the light emitting diode chipsbefore or after being divided into individual light emitting diode chipunits.

Referring to FIG. 10, a wavelength conversion layer 45 is formed on thelight emitting diodes separated from each other. The wavelengthconversion layer 45 may be formed by coating a phosphor-containing resinonto the light emitting diodes using a printing technique, or by coatingthe substrate 21 with phosphor powder using an aerosol apparatus. Forexample, aerosol deposition can form a thin phosphor layer with auniform thickness on the light emitting diodes, thereby improving coloruniformity of light emitted from the light emitting diodes. As a result,the light emitting diodes according to the embodiments of the disclosedtechnology are completed and may be bonded to the corresponding pads 53a, 53 b of the printed circuit board 51 by solder pastes, as shown inFIG. 1.

In this embodiment, the first and second electrode pad regions 43 a and43 b exposed by the upper insulation layer 41 are directly mounted onthe printed circuit board. However, it should be understood that thedisclosed technology is not limited thereto. Alternatively, additionalelectrode patterns are formed on the electrode pad regions 43 a and 43 bto form further enlarged pad regions. In this case, however, anadditional photomask for formation of the electrode patterns may beused.

FIG. 11(a) to FIG. 14(c) are views illustrating a method of fabricatinga light emitting diode in accordance with another embodiment of thedisclosed technology, and in each figure, (a) is a plan view, (b) is across-sectional view taken along line A-A, and (c) is a cross-sectionalview taken along line B-B.

In the embodiments described above, the mesa M is formed after thereflective electrode structure 35 is formed. In the presentimplementations, the mesa M is formed before the reflective electrodestructure 35 is formed.

First, referring to FIG. 11, as described with reference to FIG. 2, afirst conductive-type semiconductor layer 23, an active layer 25 and asecond conductive-type semiconductor layer 27 are formed on a substrate21. Then, the mesa M is formed by a patterning process. The mesa M issimilar to that described above in FIG. 5, and a detailed descriptionthereof will be omitted.

Referring to FIG. 12, a pre-oxidation layer 29 is formed to cover thefirst conductive-type semiconductor layer 23 and the mesa M. Thepre-oxidation layer 29 may be formed of or include the same material bythe same process as those described with reference to FIG. 2. Aphotoresist pattern 30 having openings 30 a is formed on thepre-oxidation layer 29. The openings 30 a of the photoresist pattern 30are placed in an upper region of the mesa M. The photoresist pattern 30is the same as that described with reference to FIG. 2 except that thephotoresist pattern 30 is formed on the substrate 21 having the mesa Mformed thereon, and a detailed description thereof will be omitted.

Referring to FIG. 13, the pre-oxidation layer 29 is subjected to etchingthrough the photoresist pattern 30 used as an etching mask, so thatopenings 29 a are formed to expose the second conductive-typesemiconductor layer 27 therethrough.

Referring to FIG. 14, as described in detail with reference to FIG. 4,the reflective electrode structure 35 is formed on each mesas M by alift-off technique. Then, light emitting diodes can be fabricatedthrough similar processes to the processes described above withreference to FIG. 6 to FIG. 11.

According to this embodiment, since the mesa M is formed prior to thereflective electrode structure 35, the pre-oxidation layer 29 can remainon side surfaces of the mesas M and in regions between the mesas M.Then, the pre-oxidation layer 29 is covered by the lower insulationlayer 39 and is subjected to patterning together with the lowerinsulation layer 39.

FIG. 15 is a plan view of a light emitting diode 200 in accordance withan embodiment of the disclosed technology, FIG. 16 is a cross-sectionalview taken along line A-B-B′-A′ of FIG. 15, FIG. 17 is a cross-sectionalview taken along line C-C′ of FIG. 15, and FIG. 18 is an enlarged viewof part I of FIG. 16.

Referring to FIG. 15 to FIG. 18, the light emitting diode 200 includes afirst conductive-type semiconductor layer 111, a mesa M including anactive layer 112 and a second conductive-type semiconductor layer 113, afirst insulation layer 130, a first electrode 140, and a secondinsulation layer 150, and may further include a growth substrate 101 anda second electrode 120.

The growth substrate 101 may be selected from any substrate that allowsgrowth of the first conductive-type semiconductor layer 111, the activelayer 112 and the second conductive-type semiconductor layer 113thereon, and may include, for example, a sapphire substrate, a siliconcarbide substrate, a gallium nitride substrate, an aluminum nitridesubstrate, or a silicon substrate, and the like. In someimplementations, the growth substrate 101 may be or include a patternedsapphire substrate (PSS). The growth substrate 101 may include a slantedside surface, thereby improving extraction of light generated in theactive layer 112.

The second conductive-type semiconductor layer 113 may be disposed onthe first conductive-type semiconductor layer 111, and the active layer112 may be interposed between the first conductive-type semiconductorlayer 111 and the second conductive-type semiconductor layer 113. Thefirst conductive-type semiconductor layer 111, the active layer 112, andthe second conductive-type semiconductor layer 113 may include III-Vbased compound semiconductors, for example, a nitride-basedsemiconductor such as (Al, Ga, In)N. The first conductive-typesemiconductor layer 111 may include n-type dopants (for example, Si) andthe second conductive-type semiconductor layer 113 may include p-typedopants (for example, Mg), or vice versa. The active layer 112 mayinclude a multi-quantum well (MQM) structure. Upon application offorward bias to the light emitting diode 200, light is emitted from theactive layer 112 through recombination of electrons and holes therein.The first conductive-type semiconductor layer 111, the active layer 112,and the second conductive-type semiconductor layer 113 may be grown onthe growth substrate 101, for example, by metal organic chemical vapordeposition (MOCVD), molecular bean epitaxy (MBE), or the like.

The light emitting diode 200 may include at least one mesa M thatincludes the active layer 112 and the second conductive-typesemiconductor layer 113. Referring to FIG. 15, the mesa M may include aplurality of protrusions separated from one another. The light emittingdiode 200 may include a plurality of mesas M separated from one another,without being limited thereto. The side surface of the mesa M may becomea slanted side surface by a technology such as photoresist reflow, andthe slanted side surface of the mesa M can improve luminous efficacy oflight generated from the active layer 112.

The first conductive-type semiconductor layer 111 may include a firstcontact region R₁ and a second contact region R₂ exposed through themesa M. Since the mesa M is formed by removing the active layer 112 andthe second conductive-type semiconductor layer 113 disposed on the firstconductive-type semiconductor layer 111, a portion excluding the mesa Mbecomes a contact region, which is an exposed upper surface of the firstconductive-type semiconductor layer 111. The first electrode 140described below may be electrically connected to the firstconductive-type semiconductor layer 111 by contacting the first contactregion R₁ and the second contact region R₂. The first contact region R₁may be disposed around the mesa M along an outer periphery of the firstconductive-type semiconductor layer 111, specifically, along an outerperiphery of the upper surface of the first conductive-typesemiconductor layer between the mesa M and the side surface of the lightemitting diode 200. The second contact region R₂ may be at leastpartially surrounded by the mesa M. For example, referring to FIG. 15and FIG. 16, the first contact region R₁ may be disposed near sidesurfaces of the first conductive-type semiconductor layer 111, and thesecond contact region R2 may be disposed between the protrusions of themesa M to be partially surrounded by the mesa M. Although not shown inthe drawings, when the light emitting diode includes a plurality ofmesas, the second contact region R₂ may be disposed between theplurality of mesas. Alternatively, the second contact region R₁ may beentirely surrounded by the mesa M. With this structure, the lightemitting diode allows electric current to flow through the outerperiphery and the center of the light emitting diode 200, therebyenabling efficient current spreading.

A length of the second contact region R₂ in a major axis direction maybe 0.5 times or more the length of one side of the light emitting diode200. With this structure, a contact area between the first electrode 140and the first conductive-type semiconductor layer 111 can be increasedsuch that electric current flowing from the first electrode 140 to thefirst conductive-type semiconductor layer 111 can be more efficientlyspread, thereby further reducing forward voltage.

The first contact region R₁ and the second contact region R₂ may beformed by photolithography and etching. For example, an etching regionis defined using a photoresist, and the first contact region R₁ and thesecond contact region R₂ may be formed by etching the secondconductive-type semiconductor layer 113 and the active layer 112 using adry etching process such as ICP.

The second electrode 120 is disposed on the second conductive-typesemiconductor layer 113 and may be electrically connected to the secondconductive-type semiconductor layer 113. The second electrode 120 isformed on the mesa M and may have the same shape as the mesa M. Thesecond electrode 120 may include a reflective metal layer 121 and mayfurther include a barrier metal layer 122, which covers an upper surfaceand a side surface of the reflective metal layer 121. For example, thebarrier metal layer 122 may be formed to cover the upper surface and theside surface of the reflective metal layer 121 by forming a pattern ofthe reflective metal layer 121 and then forming the barrier metal layer122 thereon. For example, the reflective metal layer 121 may be formedby deposition and patterning of Ag, Ag alloy, Ni/Ag, NiZn/Ag, or TiO/Aglayer. In some implementations, the barrier metal layer 122 may beformed of or include Ni, Cr, Ti, Pt, or Au or combinations thereof,specifically, a combination layer formed of or includingNi/Ag/[Ni/Ti]²/Au/Ti sequentially stacked on an upper surface of thesecond conductive-type semiconductor layer 113. In some implementations,at least a portion of the upper surface of the second electrode 120 mayinclude a 300A thick Ti layer. With the structure wherein the uppersurface of the second electrode 120 contacting the first insulationlayer is composed of or includes the Ti layer, the light emitting diode200 has improved bonding strength between the second electrode 120 andthe first insulation layer 130 described below, thereby providingimproved reliability. The reflective metal layer 121 prevents diffusionor contamination of a metallic material. Furthermore, the secondelectrode 120 may include a transparent conductive layer such as indiumtin oxide (ITO), zinc oxide (ZnO), and the like. ITO is composed of orincludes a metal oxide having high light transmittance and thus canimprove luminous efficacy by suppressing absorption of light by thesecond electrode 120. An electrode protective layer 160 may be disposedon the second electrode 120. As described above with reference to FIG.15 and FIG. 16, the electrode protective layer 160 may be formed of orinclude the same material as the first electrode 140, without beinglimited thereto.

The first insulation layer 130 may be disposed between the firstelectrode 140 and the mesa M. The first electrode 140 may be insulatedfrom the mesa M through the first insulation layer 130, and the firstelectrode 140 may be insulated from the second electrode 120. The firstinsulation layer 130 may partially expose the first contact region R₁and the second contact region R₂. Specifically, the first insulationlayer 130 may have an opening 130 a, through which the second contactregion R₂ is partially exposed, and may cover only a portion of thefirst contact region R₁ between the outer periphery of the firstconductive-type semiconductor layer 111 and the mesa M such that atleast a portion of the first contact region R₁ is exposed. Referring toFIG. 15 and FIG. 16, the first insulation layer 130 may be disposedalong the outer periphery of the second contact region R₂. At the sametime, the first insulation layer 130 may be restrictively disposed closeto the mesa M to be positioned more inward than an adjoining regionbetween the first contact region R₁ and the first electrode 140.Specifically, the first insulation layer 130 may be restrictivelydisposed more inside the light emitting diode 200 rather than theadjoining region between the first contact region R₁ and the firstelectrode 140. With this structure, the light emitting diode can have anincreased contact area between the first electrode 140 and the firstconductive-type semiconductor layer 111 without decreasing a lightemitting area. Furthermore, in a process of dicing light emitting diodes200 on a wafer into individual light emitting diodes 200, the firstinsulation layer 130 disposed along the outer periphery of the firstconductive-type semiconductor layer 111 can be prevented from cracking.Accordingly, it is possible to prevent delamination force of the firstelectrode 140 or a second insulation layer 150 described below fromweakening due to infiltration of moisture or contaminants throughcracks, and to prevent contamination of the first electrode, therebyimproving reliability of the light emitting diode 200. The firstinsulation layer 130 may have an opening 130 b exposing the secondelectrode 120 described below. The second electrode 120 may beelectrically connected to a pad or bump through the opening 130 b.

As shown in FIG. 18, the first insulation layer 130 may include apreliminary insulation layer 131 and a main insulation layer 132.

The preliminary insulation layer 131 may be formed on the upper surfaceof the mesa (m) and the first conductive-type semiconductor layer 111 soas to cover at least a region in which the second electrode 120 will beformed and at least a portion of an exposed region of the firstconductive-type semiconductor layer 111. Furthermore, the preliminaryinsulation layer 131 may further cover the side surface of the mesa Mand may partially cover the upper surfaces of the mesas M. Thepreliminary insulation layer 131 may contact the second electrode 120 ormay be separated therefrom. In the structure wherein the preliminaryinsulation layer 131 is separated from the second electrode 120, thesecond conductive-type semiconductor layer 113 may be partially exposedbetween the preliminary insulation layer 131 and the second electrode120. The preliminary insulation layer 131 may include SiO₂, SiNx, orMgF₂, and the like. Further, the preliminary insulation layer 131 mayinclude multiple layers, or a distributed Bragg reflector in whichmaterials having different indices of refraction are alternately stackedone above another.

In some implementations, the preliminary insulation layer 131 may beformed before formation of the second electrode 120, after formation ofthe second electrode 120, or during formation of the second electrode120. For example, when the second electrode 120 includes a conductiveoxide layer and a reflective layer disposed on the conductive oxidelayer and including a metal, the preliminary insulation layer 131 may beformed after formation of the conductive oxide layer on the secondconductive-type semiconductor layer 225 and before formation of thereflective layer. At this time, the conductive oxide layer forms ohmiccontact with the second conductive-type semiconductor layer 225 and thepreliminary insulation layer 131 may be formed to a thickness of 400 Åto 2000 Å. In other implementations, the preliminary insulation layer131 may be formed before formation of the second electrode 120. In theseimplementations, the second electrode 120 forms ohmic contact with thesecond conductive-type semiconductor layer 113 and may include areflective layer formed of or including a metallic material. In theseimplementations, since the preliminary insulation layer 131 is formedbefore formation of the reflective layer including a metallic material,it is possible to prevent reduction in reflectivity of the reflectivelayer and increase in resistance due to interdiffusion of materialsbetween the reflective layer and a light emitting structure 220.Furthermore, it is possible to prevent short circuit due to remainingmaterials on a portion at which the second electrode 120 is not formedduring formation of the reflective layer including a metallic material.

The main insulation layer 132 may be disposed to cover the preliminaryinsulation layer 131. The main insulation layer 132 may be formed by asuitable deposition method such as PECVD, or e-beam evaporation, and thelike. The main insulation layer 132 may be formed in a shape as shown inFIG. 12 through patterning after being formed to cover the entirety ofthe first conductive-type semiconductor layer 111, the mesa M and thesecond electrode 120. Patterning may include photolithographic etchingor lift-off. The main insulation layer 132 may include SiO₂, SiNx, orMgF₂, and the like. Furthermore, the main insulation layer 132 mayinclude multiple layers, or a distributed Bragg reflector in whichmaterials having different indices of refraction are alternately stackedone above another. Further, the main insulation layer 132 may be thickerthan the preliminary insulation layer 131, and may have a thickness of,for example, 1,000 Å to 18,000 Å.

As described above, the first insulation layer 130 may be formed in ashape as shown in FIG. 15 to FIG. 18 by etching. At this time, duringetching, a portion of the upper surface of the second electrode 120 isremoved such that the second electrode 120 has a reduced thickness.Specifically, the surface of the second electrode 120 exposed throughthe opening 130 b of the first insulation layer 130 can be removed to apredetermined thickness by etching. More specifically, the Ti layerincluding the exposed surface of the second electrode 120 can be removedby etching. Accordingly, an adjoining region between the upper surfaceof the second electrode 120 and the first insulation layer 130 canmaintain good bonding strength through the remaining Ti layer, which isnot removed and corresponds to a portion of the upper surface of thesecond electrode 120 contacting the first insulation layer 130. At thesame time, in other regions of the second electrode 120 to whichexternal current is applied, connection resistance can be lowered due toremoval of the Ti layer, whereby the light emitting diode can have areduced forward voltage.

After the first insulation layer 130 is formed in a shape as shown inFIG. 15 to FIG. 18 by etching, the exposed upper surface of the firstconductive-type semiconductor layer 111 may be additionally etched.Specifically, after formation of the main insulation layer 132, regionsof the first contact region R₁ and the second contact region R₂ notcovered by the first insulation layer 130 may be etched. Accordingly, aportion of the first conductive-type semiconductor layer 111 notdisposed under the first insulation layer 130 may have a smallerthickness than a portion of the first conductive-type semiconductorlayer 111 disposed under the first insulation layer 130. Furthermore,particles derived from inert gas such as CF₄ and the like used inetching of the first insulation layer 130 and remaining on the exposedregion of the first conductive-type semiconductor layer 111 can beremoved. Accordingly, bonding strength between the first electrode 140and the first conductive-type semiconductor layer 111 can be improvedand contact resistance between the first electrode 140 and the firstconductive-type semiconductor layer 111 can be reduced.

Referring to FIG. 18, since the preliminary insulation layer 131 is notdisposed on the second electrode 120 and extends from the upper surfaceof the second conductive-type semiconductor layer 113 to cover a portionof the upper surface of the first conductive-type semiconductor layer111, thickness 130T₁ of the first insulation layer 130 disposed on theupper surface of the second electrode 120 may be smaller than thickness130T₂ of the first insulation layer 130 disposed on the upper surface ofthe second conductive-type semiconductor layer 113. Further, thethickness 130T₂ of the first insulation layer 130 disposed on the uppersurface of the second conductive-type semiconductor layer 113 may be thesame as thickness 130T₃ of the first insulation layer 130 disposed onthe upper surface of the first conductive-type semiconductor layer 111.Accordingly, with the structure wherein the first insulation layer 130can cover the side surface of the mesa M without decreasing thethickness thereof, the light emitting diode can prevent infiltration ofexternal contaminants while preventing damage to the first insulationlayer 130 on the side surface of the mesa M.

The first electrode 140 may be disposed on the first insulation layer130. Specifically, the first electrode 140 may cover most of the firstinsulation layer 130. The first electrode 140 may adjoin at least aportion of the first contact region R₁ and at least a portion of thesecond contact region R₂. With this structure, the first electrode 140can be electrically connected to the first conductive-type semiconductorlayer 111. The first electrode 140 may expose an outer periphery of thefirst contact region R₁. Referring to FIG. 15 and FIG. 16, the adjoiningregion between the first contact region R₁ and the first electrode 140may be disposed closer to the mesa M than the adjoining region betweenthe first contact region R₁ and the second insulation layer 150described below. Specifically, the adjoining region between the firstcontact region R₁ and the first electrode 140 may be disposed furtherinside the light emitting diode 200 than the adjoining region betweenthe first contact region R₁ and the second insulation layer 150described below. In this structure, since the first electrode 140 is notexposed from a side surface of the light emitting diode 200, the firstelectrode 140 can be effectively protected from external moisture andthe like. Furthermore, the first electrode 140 may adjoin a portion ofthe second contact region R₂ and an interface between the firstelectrode 140 and the second contact region R₂ may be a linear plane.

A first linewidth L₁, which is a linewidth of the adjoining regionbetween the first contact region R₁ and the first electrode 140, may begreater than a second linewidth L₂, which is a linewidth of theadjoining region between the second contact region R₂ and the firstelectrode 140. In this structure, a contact area between the firstelectrode 140 and the first conductive-type semiconductor layer 111through the first contact region R₁ is relatively increased and thelight emitting diode 200 can have a reduced forward voltage.Furthermore, the light emitting diode allows more efficient currentspreading in the horizontal direction, thereby improving luminousefficacy. Specifically, the first linewidth L₁ may be greater than 10 μmand the second linewidth L₂ may be 10 μm or less. For example, the firstlinewidth L₁ may be 11 μm and the second linewidth L2 may be 10 μm.

As shown in the drawings, the first electrode 140 may be disposed on thesecond electrode 120 described below through the opening 130 b, as inone example of the electrode protective layer 160. At the same time, thefirst electrode 140 contacting the first contact region R₁ and thesecond contact region R₂ may be electrically insulated from theelectrode protective layer 160 on the second electrode 120 by the secondinsulation layer 150 described below. In this structure, when solderscomposed of AuSn or the like are used for electrical connection, thefirst electrode 140 can prevent the solders from diffusing into thesecond electrode 120 and a step between the first electrode 140 and thesecond electrode 120 can be reduced, thereby allowing the light emittingdiode 200 to be more stably attached to a circuit member such as aprinted circuit board.

The first electrode 140 may include a highly reflective metal layer suchas an Al layer, and the highly reflective metal layer may be formed on abonding layer such as a Ti, Cr or Ni layer. Furthermore, a protectivelayer composed of or including a single layer or multiple layers of Ni,Cr, or Au, and the like may be formed on the highly reflective metallayer. The first electrode 140 may have a multilayer structure of, forexample, Cr/Ti/Al/Ti/Ni/Au. Specifically, the first electrode 140 may beor include a laminate layer of Cr/Al/[Ti/Ni]²/Ti/Ni/Au/Ti sequentiallystacked on the first conductive-type semiconductor layer 111. Morespecifically, an upper surface of the first electrode 140 may include a100 Å thick Ti layer. With the structure wherein the upper surface ofthe first electrode 140 is composed of or including the Ti layer, thelight emitting diode 200 can have improved bonding strength between thefirst electrode 140 and the second insulation layer 150 described below,thereby providing improved reliability. The first electrode 140 may beformed through deposition and patterning of a metallic material.

The second insulation layer 150 may adjoin a portion of the firstcontact region R₁. Specifically, the second insulation layer 150 maycover a portion of the first contact region R₁ exposed through the firstelectrode 140. Further, the second insulation layer 150 may cover atleast a portion of the first electrode 140. The second insulation layer150 may have an opening 150 a exposing the first electrode 140 and anopening 150 b exposing the second electrode 120 described below. In thestructure wherein the light emitting diode 200 includes the electrodeprotective layer 160, the second insulation layer 150 may be interposedbetween the first electrode 140 and the electrode protective layer 160.Accordingly, insulation between the first electrode 140 and theelectrode protective layer 160 can be further secured. The secondinsulation layer 150 may be formed by depositing an oxide insulationlayer, a nitride insulation layer, or a polymer such as polyimide,Teflon® or Parylene on the first electrode 140, followed by patterning.

The second insulation layer 150 may be formed by a suitable depositionmethod such as PECVD, or e-beam evaporation, and the like. The secondinsulation layer 150 may be formed in a shape as shown in FIG. 15 toFIG. 18 through patterning after being formed to cover the entirety ofthe first conductive-type semiconductor layer 111 and the firstelectrode 140. Patterning may include photolithographic etching orlift-off.

During patterning of the second insulation layer 150, a portion of theupper surface of the first electrode 140 is removed such that the firstelectrode 140 has a reduced thickness. Specifically, the surface of thefirst electrode 140 exposed through the openings 150 a, 150 b of thesecond insulation layer 150 can be removed to a predetermined thicknessby etching. More specifically, the Ti layer including the exposedsurface of the second electrode 140 can be removed by etching.Accordingly, an adjoining region between the upper surface of the firstelectrode 140 and the second insulation layer 150 can maintain goodbonding strength through the remaining Ti layer, which is not removedand corresponds to a portion of the upper surface of the first electrode140 contacting the second insulation layer 150. At the same time, inother regions of the first electrode 140 connected to an externalelectrode via solders and the like, connection resistance can be lowereddue to removal of the Ti layer, whereby the light emitting diode canhave a reduced forward voltage. The second insulation layer 150 maycover an overall area of a side surface of the first conductive-typesemiconductor layer 111 and a portion of a side surface of the growthsubstrate 101. With this structure, the light emitting diode 200 canprotect the first conductive-type semiconductor layer 111 from externalmoisture or impact and can prevent an interface between the growthsubstrate 101 and the first conductive-type semiconductor layer 111 fromsplitting, thereby providing improved reliability.

The second insulation layer 150 may cover at least a portion of theslanted side surface of the growth substrate 101. With this structure,the second insulation layer 150 can be effectively attached to thegrowth substrate 101, thereby increasing delamination force whileimproving reliability of the light emitting diode 200. The slantedsurface may be formed in the course of allowing a laser beam to enterthe growth substrate in the process of dicing a wafer into individuallight emitting diodes 200.

FIG. 19 is a sectional view of a light emitting diode in accordance withan embodiment of the disclosed technology and a circuit member on whichthe light emitting diode is mounted, FIG. 20 is an enlarged sectionalview of part I₂ of FIG. 19, FIG. 21 is an enlarged sectional view ofpart I₃ of FIG. 20, and FIG. 22 is a sectional view illustrating astructure wherein the light emitting diode in accordance with anembodiment of the disclosed technology is mounted on a circuit member.

Referring to FIG. 19, a plurality of light emitting diodes 200 may bemounted on a circuit member 300 and may be used as a single module. Thecircuit member 300 may include a printed circuit board (PCB), withoutbeing limited thereto. As shown in FIG. 19, the circuit member 300 mayinclude a base 310 and interconnection lines 321 and 322, but is notlimited to the shape shown in FIG. 19.

Referring to FIG. 20, the light emitting diode 200 may be mounted on thecircuit member through pads 170 and 180. Specifically, the pads 170 and180 may be interposed between the light emitting diode 200 and theinterconnection lines 321 and 322 of the circuit member. The pads 170and 180 may include solders or a eutectic metal, without being limitedthereto. Specifically, AuSn may be used as the eutectic metal.

Additionally referring to FIG. 21, the pads 170 and 180 may contact thefirst electrode 140 and the second electrode 120, respectively or if theelectrode protective layer 160 is disposed on the second electrode 120,the pads 170 and 180 may contact the first electrode 140 and theelectrode protective layer 160, respectively. Since the Ti layer 140 aexposed through the first electrode 140 and the second electrode 120 isremoved by etching upon formation of the first insulation layer 130 andthe second insulation layer 150, the pads 170 and 180 can contact thefirst electrode 140 and the second electrode 120, respectively, fromwhich the Ti layer 140 a is removed. Specifically, since the Ti layer140 a is removed from the first electrode 140 and the second electrode120, an Au layer 140 b can be exposed to contact the pads 170 and 180.Further, in the structure wherein the electrode protective layer 160 isdisposed on the second electrode 120 and is formed of or includes thesame material as the first electrode 140, the Ti layer of the electrodeprotective layer 160 may also be removed, such that the exposed Au layercontacts the pad 180.

Referring to FIG. 22, the pads 170 and 180 may include a eutectic metal.In this implementation, the pads 170 and 180 may be formed of or includean Au-containing material, for example, AuSn. Accordingly, since Aucomponents of the pads 170 and 180 can contact the first electrode 140and the second electrode 120, or the first electrode 140 and the Aulayer of the electrode protective layer 160, bonding strength betweenthe light emitting diode 200 and the pads 170, 180 can be increased.Accordingly, the circuit member having the light emitting diode 200mounted thereon can have improved reliability.

FIG. 23 is a plan view of a light emitting diode 201 in accordance withan embodiment of the disclosed technology, FIG. 24 is a cross-sectionalview taken along line A-B-B′-A′ of FIG. 23, and FIG. 25 is a side viewof the light emitting diode 201 of FIG. 23. The light emitting diode 201shown in FIG. 23 is similar to the light emitting diode 200 describedwith reference to FIG. 15 to FIG. 18 except that the light emittingdiode 201 includes a second insulation layer 150 separated from an outerperiphery of a first conductive-type semiconductor layer 111 and agrowth substrate 101 includes at least one reformed region 101R.

Specifically, the growth substrate 101 may include at least one reformedregion 101R that extends from at least one side surface of the growthsubstrate 101 in the horizontal direction and has a stripe shape. Thereformed region 101R may be formed in the process of providingindividual light emitting diodes through division of the growthsubstrate 101. For example, the reformed region 101R may be formedthrough internal machining of the growth substrate. A scribing plane maybe formed inside the growth substrate 101 by internal laser machining.At this time, a distance from the reformed region 101R to a lowersurface of the growth substrate 101 may be smaller than a distance fromthe reformed region 101R to an upper surface of the growth substrate101. Considering light emitted through the side surface of the lightemitting diode 201, laser machining is performed mainly with respect toa lower side of the growth substrate 101 such that the reformed region101R is formed relatively close to the lower side thereof, therebyimproving efficiency in extraction of light generated from the activelayer 112. Furthermore, when the reformed region 101R is formed near thefirst conductive-type semiconductor layer 111, there can be a problem interms of electrical characteristics due to damage to a nitridesemiconductor during laser machining. Accordingly, with the structurewherein the reformed region 101R is formed relatively close to the lowerside of the growth substrate 101, it is possible to preventdeterioration in reliability and luminous efficacy of the light emittingdiode 201 due to damage to the nitride-based semiconductor.

The second insulation layer 150 may be disposed to be separated from theouter periphery of the first conductive-type semiconductor layer 111.Specifically, the second insulation layer 150 may be disposed in otherregions excluding the side surface of the first conductive-typesemiconductor layer 111 and the side surface of the growth substrate101, and may be separated a predetermined distance from the outerperiphery of the first conductive-type semiconductor layer 111.Accordingly, it is possible to prevent damage to the first insulationlayer 150 due to stress applied to interfaces between individual lightemitting diodes during the process of providing the individual lightemitting diodes through division of the growth substrate 101.

FIG. 26 is a plan view of a light emitting diode 202 in accordance withan embodiment of the disclosed technology and FIG. 27 is across-sectional view taken along line A-B-B′-A′ of FIG. 26.

The light emitting diode 202 shown in FIG. 26 and FIG. 27 is similar tothe light emitting diode 200 described with reference to FIG. 15 andFIG. 16 except that the adjoining region between the first contactregion R₁ and the first electrode 140 is disposed along the outerperiphery of the overall upper surface of the first conductive-typesemiconductor layer. Specifically, the adjoining region between thefirst contact region R₁ and the first electrode 140 may be disposed nearall four side surfaces of the first conductive-type semiconductor layer111 and may completely surround the mesa M. In this embodiment, acontact area between the first electrode 140 and the firstconductive-type semiconductor layer 111 can be increased such thatelectric current flowing from the first electrode 140 to the firstconductive-type semiconductor layer 111 can be more efficiently spread,thereby further reducing forward voltage.

FIG. 28 is a plan view of a light emitting diode 203 in accordance withan embodiment of the disclosed technology, FIG. 29 is a cross-sectionalview taken along line A-A′ of FIG. 28, and FIG. 30 is a cross-sectionalview taken along line B-B′ of FIG. 28.

The light emitting diode 203 shown in FIG. 28 to FIG. 30 is similar tothe light emitting diode 200 described with reference to FIG. 15 andFIG. 16 excluding the shape of the mesa M.

Specifically, the mesa M of the light emitting diode 200 shown in FIG.15 and FIG. 16 includes the plurality of protrusions protruding towardsone side surface of the light emitting diode 200 by way of example. Onthe contrary, the light emitting diode 203 shown in FIG. 28 to FIG. 30may include not only a plurality of protrusions protruding towards oneside of the first conductive-type semiconductor layer 111 but also aplurality of protrusions protruding towards the other side thereof.

Accordingly, a second contact region R₂ partially surrounded by the mesaM can be increased. That is, it is possible to secure the second contactregion R₂ disposed between the pluralities of protrusions protrudingtowards the one side of the first conductive-type semiconductor layer111 and the other sides thereof. With this structure, not only in aregion near the one side of the first conductive-type semiconductorlayer 111 but also in a region near the other side thereof, efficientcurrent movement can be achieved between the second electrode 120 on theprotrusions and the first electrode 140 on the second contact region R₂.Accordingly, light emission from the region adjacent the other side canbe improved.

FIG. 31 is an exploded perspective view of an exemplary lightingapparatus to which a light emitting diode in accordance with anembodiment of the disclosed technology is applied.

Referring to FIG. 31, the lighting apparatus according to thisembodiment includes a diffusive cover 1010, a light emitting diodemodule 1020, and a body 1030. The body 1030 may receive the lightemitting diode module 1020 and the diffusive cover 1010 may be disposedon the body 1030 to cover an upper portion of the light emitting diodemodule 1020.

The body 1030 may have any structure so long as the body can receive andsupport the light emitting diode module 1020 to supply electric power tothe light emitting diode module 1020. For example, the body 1030 mayinclude a body case 1031, a power supply 1033, a power source case 1035,and a power connector 1037, as shown in FIG. 31.

The power supply 1033 is received in the power source case 1035 to beelectrically connected to the light emitting diode module 1020 and mayinclude at least one integrated circuit (IC) chip. The IC chip canregulate, change or control characteristics of power supplied to thelight emitting diode module 1020. The power source case 1035 may receiveand support the power supply 1033, and may be disposed inside the bodycase 1031, with the power supply 1033 secured inside the power sourcecase 1035. The power connector 115 is provided to a lower end of thepower source case 1035 and is coupled to the power source case 1035.With this structure, the power connector 115 is electrically connectedto the power supply 1033 inside the power source case 1035 and may actas a passage through which external power can be supplied to the powersupply 1033.

The light emitting diode module 1020 includes a substrate 1023 and alight emitting diode 1021 disposed on the substrate 1023. The lightemitting diode module 1020 may be disposed at an upper portion of thebody case 1031 and electrically connected to the power supply 1033.

The substrate 1023 may be selected from any substrate so long as thesubstrate can support the light emitting diode 1021, and may be orinclude, for example, a printed circuit board includinginterconnections. The substrate 1023 may have a shape corresponding to asecuring portion at the upper portion of the body case so as to bestably secured to the body case 1031. The light emitting diode 1021 mayinclude at least one of the light emitting diodes according to the aboveembodiments.

The diffusive cover 1010 is disposed above the light emitting diode 1021and is secured to the body case 1031 to cover the light emitting diode1021. The diffusive cover 1010 may be formed of or include a lighttransmitting material and light orientation characteristics of thelighting apparatus can be regulated through adjustment of the shape andlight transmittance of the diffusive cover 1010. Accordingly, thediffusive cover 1010 may be modified in various ways depending uponpurposes and applications of the lighting apparatus.

FIG. 32 is a sectional view of an exemplary display to which a lightemitting diode in accordance with an embodiment of the disclosedtechnology is applied.

The display according to this embodiment includes a display panel 2110,a backlight unit BLU1 supplying light to the display panel 2110, and apanel guide 2100 supporting a lower edge of the display panel 2110.

The display panel 2110 may be, for example, a liquid crystal displaypanel including a liquid crystal layer, without being limited thereto.The display panel 2110 may be provided at an edge thereof with gatedrive PCBs for supplying drive signals to a gate line. In someimplementations, the gate drive PCBs 2112 and 2113 may be formed on athin film transistor substrate instead of a separate PCB.

The backlight unit BLU1 includes a light source module including atleast one substrate 2150 and a plurality of light emitting diodes 2160.The backlight unit BLU1 may further include a bottom cover 2180, adiffusive sheet 2170, a diffusive plate 2131, and optical sheets 2130.

The bottom cover 2180 is open at an upper side thereof and may receivethe substrate 2150, the light emitting diodes 2160, the diffusive sheet2170, the diffusive plate 2131 and the optical sheets 2130. In addition,the bottom cover 2180 may be coupled to the panel guide 2100. Thesubstrate 2150 may be disposed at a lower side of the diffusive sheet2170 to be surrounded by the diffusive sheet 2170. Alternatively, in thestructure wherein a surface of the substrate 2150 is coated with areflective material, the substrate 2150 may be disposed on the diffusivesheet 2170. In some implementations, a plurality of substrates 2150 maybe arranged parallel to each other. However, it should be understoodthat the disclosed technology is not limited thereto and the substrate2150 may be realized by a single substrate.

The light emitting diodes 2160 may include at least one of the lightemitting diodes according to the embodiments described above. The lightemitting diodes 2160 may be regularly arranged in a predeterminedpattern on the substrate 2150. Furthermore, a lens 2210 is disposed oneach of the light emitting diodes 2160, thereby improving uniformity oflight emitted from the plurality of light emitting diodes 2160.

The diffusive plate 2131 and the optical sheets 2130 are disposed abovethe light emitting diodes 2160. Light emitted from the light emittingdiodes 2160 may be supplied in the form of surface light to the displaypanel 2110 through the diffusive plate 2131 and the optical sheets 2130.

As such, the light emitting diodes according to the embodiments of thedisclosed technology may be applied to a direct type display as in thisembodiment.

FIG. 33 is a sectional view of an exemplary display to which a lightemitting diode in accordance with an embodiment of the disclosedtechnology is applied.

A display according to this embodiment includes a display panel 3210 onwhich an image is displayed, and a backlight unit BLU2 disposed at thebackside of the display panel 3210 and supplying light. The displayincludes a frame 240 supporting the display panel 3210 and receiving thebacklight unit BLU2, and covers 3240, 3280 enclosing the display panel3210.

The display panel 3210 may be, for example, a liquid crystal displaypanel including a liquid crystal layer, without being limited thereto.The display panel 3210 may be provided at an edge thereof with gatedrive PCBs for supplying drive signals to a gate line. In someimplementations, the gate drive PCBs may be formed on a thin filmtransistor substrate instead of a separate PCB. The display panel 3210is secured by the covers 3240 and 3280 disposed at upper and lower sidesthereof, and the cover 3280 disposed at the lower side of the displaypanel may be coupled to the backlight unit BLU2.

The backlight unit BLU2 configured to supply light to the display panel3210 includes a lower cover 3270 partially open at an upper sidethereof, a light source module disposed at one side within the lowercover 3270 and a light guide plate 3250 disposed parallel to the lightsource module and converting spot light into surface light. Thebacklight unit BLU2 according to this embodiment may further includeoptical sheets 3230 disposed above the light guide plate 3250 to collectand spread light, and a reflective sheet 3260 disposed below the lightguide plate 3250 to reflect light, which travels in a downward directionof the light guide plate 3250, towards the display panel 3210.

The light source module includes a substrate 3220 and a plurality oflight emitting diodes 3110 arranged at constant intervals on one surfaceof the substrate 3220. The substrate 3220 may be selected from anysubstrate so long as the substrate can support the light emitting diodes3110 and be electrically connected to the light emitting diodes 3110,and may be or include, for example, a printed circuit board. The lightemitting diodes 3110 may include at least one of the light emittingdiodes according to the embodiments described above. Light emitted fromthe light source module enters the light guide plate 3250 to be suppliedto the display panel 3210 through the optical sheets 3230. Through thelight guide plate 3250 and the optical sheets 3230, spot light emittedfrom the light emitting diodes 3110 can be converted into surface light.

As such, the light emitting diodes according to the embodiments of thedisclosed technology may be applied to an edge type display as in thisembodiment.

FIG. 34 is a sectional view of an exemplary headlight to which a lightemitting diode in accordance with an embodiment of the disclosedtechnology is applied.

Referring to FIG. 34, the headlight includes a lamp body 4070, asubstrate 4020, a light emitting diode 4010, and a cover lens 4050. Theheadlight may further include a heat dissipation portion 4030, a supportrack 4060, and a connection member 4040.

The substrate 4020 is secured by the support rack 4060 and disposedabove the lamp body 4070 to be separated therefrom. The substrate 4020may be selected from any substrate so long as the substrate can supportthe light emitting diode 4010, and may be or include, for example, aprinted circuit board having a conductive pattern. The light emittingdiode 4010 is disposed on the substrate 4020 and may be supported andsecured by the substrate 4020. Further, the light emitting diode 4010may be electrically connected to an external power source through theconductive pattern of the substrate 4020. The light emitting diode 4010may include at least one of the light emitting diodes according to theembodiments described above.

The cover lens 4050 is placed on an optical path along which lightemitted from the light emitting diode 4010 travels. For example, asshown in FIG. 34, the cover lens 4050 may be separated from the lightemitting diode 4010 by the connection member 4040 and may be disposed ina direction in which light emitted from the light emitting diode 4010will be supplied. By the cover lens 4050, a beam angle and/or a color oflight emitted from the headlight to the outside can be regulated. On theother hand, the connection member 4040 secures the cover lens 4050 tothe substrate 4020 and is disposed to surround the light emitting diode4010 so as to act as a light guide providing a light emission path 4045.Here, the connection member 4040 may be formed of a light reflectivematerial or may be coated with the light reflective material. The heatdissipation portion 4030 may include heat dissipation fins 4031 and/or aheat dissipation fan 4033, and dissipates heat generated duringoperation of the light emitting diode 4010.

As such, the light emitting diodes according to the embodiments of thedisclosed technology may be applied to a headlight as in thisembodiment, particularly, to a vehicle headlight.

Although various embodiments have been described above, it should beunderstood that other implementations are also possible. In addition,some features of a certain embodiment may also be applied to otherembodiments in the same or similar ways without departing from thespirit and scope of the disclosed technology.

What is claimed is:
 1. A light emitting diode comprising: a firstconductive-type semiconductor layer; a mesa including a secondconductive-type semiconductor layer disposed over the firstconductive-type semiconductor layer and an active layer interposedbetween the second conductive-type semiconductor layer and the firstconductive-type semiconductor layer; and a first electrode disposed overthe mesa, wherein the first conductive-type semiconductor layercomprises a first contact region disposed around the mesa along an outerperiphery of the first conductive-type semiconductor layer; and a secondcontact region at least partially surrounded by the mesa, the firstelectrode is electrically connected to at least a portion of the firstcontact region and at least a portion of the second contact region, anda linewidth of an adjoining region between the first contact region andthe first electrode is greater than the linewidth of an adjoining regionbetween the second contact region and the first electrode.
 2. The lightemitting diode of claim 1, wherein the second contact region iselectrically connected to the first contact region.
 3. The lightemitting diode of claim 1, wherein a length of the second contact regionin a major axis direction is 0.5 times or more the length of one side ofthe light emitting diode.
 4. The light emitting diode of claim 1,wherein the linewidth of the adjoining region between the first contactregion and the first electrode is greater than 10 μm and the linewidthof the adjoining region between the second contact region and the firstelectrode is 10 μm or less.
 5. The light emitting diode of claim 1,further comprising: a first insulation layer interposed between thefirst electrode and the mesa, the first insulation layer partiallyexposing the first contact region and the second contact region.
 6. Thelight emitting diode of claim 5, wherein the first insulation layer isrestrictively disposed closer to the mesa than the adjoining regionbetween the first contact region and the first electrode.
 7. The lightemitting diode of claim 5, wherein the first electrode contacts thefirst contact region and the second contact region that are exposedthrough the first insulation layer exposing an outer periphery of thefirst contact region.
 8. The light emitting diode of claim 5, wherein aportion of the first conductive-type semiconductor layer not disposedunder the first insulation layer has a smaller thickness than a portionof the first conductive-type semiconductor layer disposed under thefirst insulation layer.
 9. The light emitting diode of claim 5, whereinthe first insulation layer disposed on an upper surface of the secondconductive-type semiconductor layer has the same thickness as the firstinsulation layer disposed on the upper surface of the firstconductive-type semiconductor layer.
 10. The light emitting diode ofclaim 1, further comprising: a second insulation layer covering thefirst electrode and the second contact region exposed through the firstelectrode.
 11. The light emitting diode of claim 10, wherein the firstelectrode includes a plurality of layers, and an upper portion of thefirst electrode contacting the second insulation layer includes a Tilayer.
 12. The light emitting diode of claim 11, wherein the secondinsulation layer comprises an opening exposing the first electrode, andan upper portion of the first electrode exposed through the opening ofthe second insulation layer includes an Au layer.
 13. The light emittingdiode of claim 12, further comprising: a first pad contacting the firstelectrode, wherein the first pad contacts the exposed Au layer.
 14. Thelight emitting diode of claim 5, further comprising: a second electrodedisposed on the second conductive-type semiconductor layer andelectrically connected to the second conductive-type semiconductorlayer, the second electrode being insulated from the first electrode bythe first insulation layer.
 15. The light emitting diode of claim 14,wherein a portion of the first insulation layer disposed on an uppersurface of the second electrode has a smaller thickness than a portionof the first insulation layer disposed on the upper surface of thesecond conductive-type semiconductor layer.
 16. The light emitting diodeof claim 14, wherein the second electrode includes a plurality oflayers, and an upper portion of the second electrode contacting thefirst insulation layer includes a Ti layer.
 17. The light emitting diodeof claim 16, wherein the first insulation layer comprises an openingexposing the second electrode, and an upper portion of the secondelectrode exposed through the opening of the first insulation layerincludes an Au layer.
 18. The light emitting diode of claim 17, furthercomprising: a second pad contacting the second electrode, wherein thesecond pad contacts the exposed Au layer.
 19. The light emitting diodeof claim 10, further comprising: a growth substrate disposed under thefirst conductive-type semiconductor layer.
 20. The light emitting diodeof claim 19, wherein the second insulation layer covers an overallregion of a side surface of the first conductive-type semiconductorlayer and a portion of a side surface of the growth substrate.
 21. Thelight emitting diode of claim 19, wherein the growth substrate comprisesat least one reformed region having a stripe shape and extending from atleast one side surface of the growth substrate in a horizontal directionthereof.
 22. The light emitting diode of claim 21, wherein the secondinsulation layer is separated from the outer periphery of the firstconductive-type semiconductor layer by a predetermined distance.
 23. Thelight emitting diode of claim 1, wherein the mesa comprises a pluralityof protrusions protruding towards one side of the first conductive-typesemiconductor layer; and a plurality of protrusions protruding towardsthe other side of the first conductive-type semiconductor layer.